Method of punching out metal



y 1950 c. HOLLERITH 2,508,758

METHQD 0F PUNCHING OUT METAL I Filed Sept. 20, 1946 44 INVENTOR,

EH/JF1L E5HULLER/TH Patented May 23, 1950 UNITED STATES FPATENT OFFICEMETHOD or our METAL 7 Charles Hollerith, Jackson, Mich. assignor toHayes Industries, Inc,; Jackson, Mich., a cornotation of MichiganApplication September 20, 1946, Serial No. 698,167

The present invention relates to improvements in metal stamping, beingparticularly concerned with the method whereby rounded edges areprovided on both the blank and the perforated strip or sheet.

Heretofore it has been the practice in blanking and formin metal sheetand strip stock to complete the blanking, shearing, and punchingoperations with a single stroke of the pun-ch and from one side of thesheet or strip only. This standard method results in a rounded edge onlyon that side of the material on the opposite side of the material fromwhich the punch operates.

According to the present invention, a method is provided for providinrounded edges on both sides of the blank as well as the perforated sheetor strip. This has been accomplished by employing two operations, thefirst operation being in the order of an embossing operation from oneside of the sheet or strip with a second and final operation a completeblanking operation from the opposite side of the sheet or strip.

Thus one of the objects of the invention is to provide an improvedmethod of obtaining round edge blanks and perforated sheet or strip.

Another object of the invention is to provide an improved method ofmetal sheet and strip blanking in which the blank and the perforatedstock are both provided with round edges on each side.

Another object of the invention is to provide an improved method ofstamping metal sheet end strip in which the perforation of the metal ispartly completed in one direction with the perforating operation beingcompleted from the opposite side.

A still further object of the invention is to provide an improved methodof forming rounded edge blanks from sheet Or strip metal by employing acombination embossing and blanking operation progressively eflected onopposite sides of a sheet or strip.

These and other objects of the invention vrill more clearly appear froma consideration of the following specification and appended claims.

In the drawings,

Fig. I is a cross-sectional view through a suitable die for carrying outmy improved method,

Fig. II is a perspective view of the metal strip upon which theoperations of the die of Fig. I have been performed, and

Fig. III is a cross-sectional view of a blank showing the rounded edges.

In Fig. I of the drawings, one suitable die construction is illustratedcapable of carrying out the principles of the present invention. As

shown, the upper and lower plates ill and 12 of a standard die cast setcarries a lower die l4 and an upper punch it for performing the firstoperation which may be termed an embossing operation, with the upper die18 and the lower punch 20 performing the second and final punchingoperation. Suitable pressure pads are indicated at 22, 24, 26 and 28.

The metal strip or sheet 30 is fed in the die shown in Fig. I from rightto left. At the lefthand side of Fig. I the metal strip 30 is shown withperforations 32, having all of the edges 34 rounded, both top andbottom. The die is shown completely closed with the blank 36 completelysheared from the strip 30 by the punch 20. In the first operation, thepunch 16 is shown having completed the embossment 38. This firstoperation rounds the edges 40 of the perforated strip as well as thelower edge 42 of the final blank.

With each stroke of the press, the embossment 38 is indexed from thefirst operation position into the inactive cavity 44 and upon the nextindex into alignment with the punch 20 where the final operation isprovided upon theembossment 38. In this position, the blank 44 iscompletely sheared from the strip 30, with this final operation roundingthe upper edges 46 of the blank and completing the rounding of the edgesof the perforations 32. It will be understood that with the productiondie construction shown in Fig. I, that each stroke of the press afterthe second index will result in the formation of a blank 44 and aperforation 32 in the sheet or strip 30.

The method herein disclosed avoids for the most part any necessity forfurther operations to remove the sharp and torn edges conventionallyresulting from punching and shearing metal. Also, it will materiallyreduce the formation of fissures and cracks in the edges of the blanksand perforated strips and sheets which cause failure of structure underoperating loads especially in the case of fabricated parts subjected toviolent vibration and fiexure. For example, it is anticipated that byemploying the method herein disclosed many holes may be punched inaircraft structure which have heretofore been drilled in order to reducestructural failures.

Having thus described my invention, what I claim as new and desire tocover by Letters Patent is:

1. A method of forming blanks and perforated ing and shearing theprotuberance out of the strip from the opposite side.

2. A method of forming blanks and perfora l7 tions with rounded edgesfrom metal sheets strips and the like, comprising the step of firstforming an embossment to provide a depression on one side of the stripand a protuberance on the opposite side of the strip, and as a finalstep the punching and shearing of the embossmentfrom the strip bypunching the protuberance back through the stripand depression.

3. A method of punching sheet metal to provide blanks andperforations,comprising the step of partially punching out a blank from one side toform a depression on that side and a cor- 4 responding protuberance onthe opposite side and then completing the punching out of the blank fromthe said opposite side.

4. A method of forming blanks and perforations in sheet metal in twooperative steps, comprising the first step of partially punching a.blank from one side of the sheet to form a depression on that side andaprotuberance on the opposite side and followed by the second step ofcompleting the separation of the blank from the i sheet by punching theprotuberance back through the sheet and depression from the saidopposite side of the sheet.

CHARLES HOLLERI'IH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date

